RE: [amsat-bb] 3/4 Wave Vertical Omni

[Tony Langdon <tlangdon@xxxxxxxxxxxxxxxxxx>]

> For the mobile Satellite operator looking for an Omni, I finally did a
> real-world antenna plot of a 3/4 wave 435 Mhz WHip over a car roof
> to see how well it matches the EZNEC predictions.  The 
> results confirm the
> almost 8 dBi gain from about 30 to 80 degrees elevation:

Sounds quite useful.  I must see why my attempt to use a 2m 1/4 wave failed
on 435 MHz.  Time to get out the FS meter. :-)

> Probably the only way to fill in the low angle is to go to a high
> gain vertical (to get 9 dBi below 30 deg) and switch between the two.
> during each pass.  But given the complexity, I just stick with the 3/4
> wave (20" vertical) since it is inherrently dual band being 

I think a switched system is the only way to get the below 30 deg coverage.
Depends on one's requirements.  As you say, the higher angles are fine for
APRS work.

> whip in the center of your car roof will serve very well as a mobile
> satellite antenna whenever the satellite is above 30 degrees, and most
> mobiles cant see much below 30 degrees anyway due to trees.. 
> (back east
> anyway...)...

Hmm, here in Melbourne, 10 degrees is usually visible from a mobile.  We
have quite flat terrain, and the western half of the city (where I'm usually
mobile) is built on a basalt plain, so the only limitation on the horizon is
the houses and the odd tree.  Further west, it's open grassland with horizon
to horizon views from a mobile. :-)

> Come join us on SUNSAT and any other satellite that may have UI
> digipeating enabled...

I'm there. :)
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